Ansible Tutorial

Introduction In this short Ansible tutorial we will go through the installation process of Ansible and its basic features. Ansible is an automation tool which allows us to manage remote servers without installing any agents on those remote machines.  Only the control machine needs to have it installed. By “remote servers” I mean not only Linux/Windows

How to test network speed using two Linux machines?

Introduction This guide will show you how you can perform a network speed test using two Linux machines. It will show you the actual network bandwidth between two points in your network. We will connect a Linux machine at each point in you network and generate traffic between them. We can use simple laptops, desktops

Tcpdump command examples.

Introduction This post is about tcpdump – packet analyzer that comes preinstalled with any modern Linux distribution. tcpdump allows us to capture packets and either display them in real time or save them to a file for later analysis. We will look at several examples of using tcpdump to learn which options it has and

Introduction to iptables

Introduction In this tutorial we will learn how to configure iptables which is a built-in Linux firewall. I will use Ubuntu 18.04 for demo, but you can use any other Linux distro. Before we get into actual configuration we will learn some theory behind iptables. iptables allows us to filter packets based on IP addresses,

Custom background image on Cisco IP Phone

Introduction This is a short article on how to create a custom background image on Cisco IP phone managed by Cisco Unified Communications Manager(CUCM). We will consider IP Phone Cisco 8851 and CUCM 11.5, but the provided instructions are applicable to any IP Phone managed by CUCM. Background Image Format The first thing we need

Shell Scripting Guide

Introduction In this guide we are going to learn how to use BASH shell scripting. Shell scripting is usually used for tasks such as file manipulation, program execution and task automation. Shell scripts contain the same commands you normally run in a terminal, it just allows you to group them together and run them in

How to create a custom recording for IVR greeting in FreePBX?

Introduction In this short tutorial we are going to create a custom recording for IVR greeting. These recordings are called Announcements/System Recordings (these terms are used interchangeably) in FreePBX. Whenever you create an IVR application you select which audio file should be played back to the callers in Announcement field. How to create a custom

How to create a systemd service?

Introduction In this guide we will create a systemd service and make it automatically start on a boot. We have already seen how we can make commands execute on a boot using cron scheduler in this post. Creating systemd service file is an alternative way of doing this, and since systemd is becoming more and

Regular Expressions

In this guide we are going to learn how to use Regular Expressions (regex) to match any pattern or text. This is often used in text editors, CLI commands(like grep or awk) and programming languages. What is regex? Regex are patterns used to match/find strings in a text. You might think that you can use